Support runes mode on @auth/sveltekit

[lucas-subli]

Goals

1. Work with Svelte 5 if runes mode is enforced

Currently it errors with:

node_modules/.pnpm/@auth+sveltekit@1.8.0_@sveltejs+kit@2.20.1_@sveltejs+vite-plugin-svelte@5.0.3_svelte@5.23.2_v_c22cw6ibutgwrkatehthzhxwee/node_modules/@auth/sveltekit/dist/components/SignIn.svelte:18:6 Cannot use `$$restProps` in runes mode
https://svelte.dev/e/legacy_rest_props_invalid]

Non-Goals

No response

Background

Svelte 5 has changed to use the runes system.
Runes are the future of Svelte, and eventually, non-Runes mode will be removed; thus, this will be a necessity.

Proposal

Migrate the existing components under @auth/sveltekit/components to user runes